Spring Boot MyBatis 通用Mapper插件集成

看本文之前，请确保你已经在SpringBoot中集成MyBatis，并能正常使用。
假设没有，那么请先移步 http://blog.csdn.net/catoop/article/details/50553714 做了解后，再按本文步骤操作。

使用MyBatis在我们通过xml集中配置SQL，并通过创建接口Mapper文件来完毕持久化DAO层（mybatis内部使用的是动态代理，所以我们不须要自己编写实现类）。

然而在实际开发中。单表操作许多，假设你也想像JPA、JDBC那样做一个所谓的BaseDao。

那么能够实现一个通用Mapper来达到目的。如今有现成的通用Mapper插件，我们无需又一次创造轮子（代码是开源的，你也能够自己在其基础上改动）。

通用Mapper插件网址：https://github.com/abel533/Mapper

---

以下是用法（本文直接将分页插件PageHelper也集成了）：
一、加入或改动pom依赖

        <!-- MyBatis -->
<!--        <dependency> -->
<!--            <groupId>org.mybatis.spring.boot</groupId> -->
<!--            <artifactId>mybatis-spring-boot-starter</artifactId> -->
<!--            <version>1.0.1-SNAPSHOT</version> -->
<!--        </dependency> -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.3.0</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>1.2.3</version>
        </dependency>
        <!-- 分页插件 -->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper</artifactId>
            <version>4.1.1</version>
        </dependency>
        <!--通用Mapper插件-->
        <dependency>
            <groupId>tk.mybatis</groupId>
            <artifactId>mapper</artifactId>
            <version>3.3.4</version>
        </dependency>

这里说一下。文章開始指定的那篇文章中直接依赖的mybatis的starter。由于本文在集成通用Mapper的时候直接使用出现了错误，所以将mybatis的starter中的Java类（它本身仅仅有2个Java类。很easy）复制到project中，凝视掉了头部的//@ConditionalOnBean(DataSource.class)，你不用去找那2个类的源代码了，以下会粘贴出来。

二、将以下4个Java类加入到project中

将文件
MybatisAutoConfiguration.java
MyBatisMapperScannerConfig.java
MybatisProperties.java
MyMapper.java
加入到 org.springboot.sample.config.mybatis 中（包名依据自己project改动）

最有一个MyMapper.java要特别注意，不要把MyMapper放到同其它Mapper一起，该类不能被当做普通Mapper一样被扫描。否则会出错。

package org.springboot.sample.config.mybatis;

import java.util.Properties;

import javax.annotation.PostConstruct;
import javax.sql.DataSource;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.SqlSessionTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.DefaultResourceLoader;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

import com.github.pagehelper.PageHelper;

/**
 * {@link EnableAutoConfiguration Auto-Configuration} for Mybatis. Contributes a
 * {@link SqlSessionFactory} and a {@link SqlSessionTemplate}.
 *
 * If {@link org.mybatis.spring.annotation.MapperScan} is used, or a configuration file is
 * specified as a property, those will be considered, otherwise this auto-configuration
 * will attempt to register mappers based on the interface definitions in or under the
 * root auto-configuration package.
 *
 * @author Eddú Meléndez
 * @author Josh Long
 */
@Configuration
@ConditionalOnClass({ SqlSessionFactory.class, SqlSessionFactoryBean.class })
//@ConditionalOnBean(DataSource.class)
@EnableConfigurationProperties(MybatisProperties.class)
@AutoConfigureAfter(DataSourceAutoConfiguration.class)
public class MybatisAutoConfiguration {

    private static Log log = LogFactory.getLog(MybatisAutoConfiguration.class);

    @Autowired
    private MybatisProperties properties;

    @Autowired(required = false)
    private Interceptor[] interceptors;

    @Autowired
    private ResourceLoader resourceLoader = new DefaultResourceLoader();

    @PostConstruct
    public void checkConfigFileExists() {
        if (this.properties.isCheckConfigLocation()) {
            Resource resource = this.resourceLoader
                    .getResource(this.properties.getConfig());
            Assert.state(resource.exists(),
                    "Cannot find config location: " + resource
                            + " (please add config file or check your Mybatis "
                            + "configuration)");
        }
    }

    @Bean(name = "sqlSessionFactory")
    @ConditionalOnMissingBean
    public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
        SqlSessionFactoryBean factory = new SqlSessionFactoryBean();
        factory.setDataSource(dataSource);
        if (StringUtils.hasText(this.properties.getConfig())) {
            factory.setConfigLocation(
                    this.resourceLoader.getResource(this.properties.getConfig()));
        } else {
            if (this.interceptors != null && this.interceptors.length > 0) {
                factory.setPlugins(this.interceptors);
            }
            factory.setTypeAliasesPackage(this.properties.getTypeAliasesPackage());
            factory.setTypeHandlersPackage(this.properties.getTypeHandlersPackage());
            factory.setMapperLocations(this.properties.getMapperLocations());
        }
        return factory.getObject();
    }

    @Bean
    @ConditionalOnMissingBean
    public SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
        return new SqlSessionTemplate(sqlSessionFactory,
                this.properties.getExecutorType());
    }

    /**
     * 分页插件
     *
     * @param dataSource
     * @return
     * @author SHANHY
     * @create  2016年2月18日
     */
    @Bean
    public PageHelper pageHelper(DataSource dataSource) {
        log.info("注冊MyBatis分页插件PageHelper");
        PageHelper pageHelper = new PageHelper();
        Properties p = new Properties();
        p.setProperty("offsetAsPageNum", "true");
        p.setProperty("rowBoundsWithCount", "true");
        p.setProperty("reasonable", "true");
        pageHelper.setProperties(p);
        return pageHelper;
    }

}

package org.springboot.sample.config.mybatis;

import java.util.Properties;

import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import tk.mybatis.spring.mapper.MapperScannerConfigurer;

/**
 * MyBatis扫描接口，使用的tk.mybatis.spring.mapper.MapperScannerConfigurer <br/>
 * 假设你不使用通用Mapper，能够改为org.xxx...
 *
 */
@Configuration
//TODO 注意。由于MapperScannerConfigurer运行的比較早。所以必须有以下的注解
@AutoConfigureAfter(MybatisAutoConfiguration.class)
public class MyBatisMapperScannerConfig {

    @Bean
    public MapperScannerConfigurer mapperScannerConfigurer() {
        MapperScannerConfigurer mapperScannerConfigurer = new MapperScannerConfigurer();
        mapperScannerConfigurer.setSqlSessionFactoryBeanName("sqlSessionFactory");
        mapperScannerConfigurer.setBasePackage("org.springboot.sample.mapper");
        Properties properties = new Properties();
        // 这里要特别注意，不要把MyMapper放到 basePackage 中。也就是不能同其它Mapper一样被扫描到。
 
        properties.setProperty("mappers", MyMapper.class.getName());
        properties.setProperty("notEmpty", "false");
        properties.setProperty("IDENTITY", "MYSQL");
        mapperScannerConfigurer.setProperties(properties);
        return mapperScannerConfigurer;
    }

}

package org.springboot.sample.config.mybatis;

import org.apache.ibatis.session.ExecutorType;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.core.io.Resource;

/**
 * Configuration properties for Mybatis.
 *
 * @author Eddú Meléndez
 */
@ConfigurationProperties(prefix = MybatisProperties.MYBATIS_PREFIX)
public class MybatisProperties {

    public static final String MYBATIS_PREFIX = "mybatis";

    /**
     * Config file path.
     */
    private String config;

    /**
     * Location of mybatis mapper files.
     */
    private Resource[] mapperLocations;

    /**
     * Package to scan domain objects.
     */
    private String typeAliasesPackage;

    /**
     * Package to scan handlers.
     */
    private String typeHandlersPackage;

    /**
     * Check the config file exists.
     */
    private boolean checkConfigLocation = false;

    /**
     * Execution mode.
     */
    private ExecutorType executorType = ExecutorType.SIMPLE;

    public String getConfig() {
        return this.config;
    }

    public void setConfig(String config) {
        this.config = config;
    }

    public Resource[] getMapperLocations() {
        return this.mapperLocations;
    }

    public void setMapperLocations(Resource[] mapperLocations) {
        this.mapperLocations = mapperLocations;
    }

    public String getTypeHandlersPackage() {
        return this.typeHandlersPackage;
    }

    public void setTypeHandlersPackage(String typeHandlersPackage) {
        this.typeHandlersPackage = typeHandlersPackage;
    }

    public String getTypeAliasesPackage() {
        return this.typeAliasesPackage;
    }

    public void setTypeAliasesPackage(String typeAliasesPackage) {
        this.typeAliasesPackage = typeAliasesPackage;
    }

    public boolean isCheckConfigLocation() {
        return this.checkConfigLocation;
    }

    public void setCheckConfigLocation(boolean checkConfigLocation) {
        this.checkConfigLocation = checkConfigLocation;
    }

    public ExecutorType getExecutorType() {
        return this.executorType;
    }

    public void setExecutorType(ExecutorType executorType) {
        this.executorType = executorType;
    }
}

package org.springboot.sample.config.mybatis;

import tk.mybatis.mapper.common.Mapper;
import tk.mybatis.mapper.common.MySqlMapper;

/**
 * 被继承的Mapper。一般业务Mapper继承它
 *
 */
public interface MyMapper<T> extends Mapper<T>, MySqlMapper<T> {
    //TODO
    //FIXME 特别注意，该接口不能被扫描到，否则会出错
}

三、属性配置文件
属性配置文件里和文章开头指定的文章一样配置。没有什么改动，以下粘贴出来：

mybatis.mapper-locations=classpath*:org/springboot/sample/mapper/sql/mysql/*Mapper.xml
mybatis.type-aliases-package=org.springboot.sample.entity

四、在业务Mapper中继承基础MyMapper接口

public interface StudentMapper extends MyMapper<Student> {

    List<Student> likeName(String name);

    Student getById(int id);

    int add(Student stu);

    String getNameById(int id);

}

然后在Service中使用就可以，后面就没什么说的了。

@Service
public class StudentService {

    @Autowired
    private JdbcTemplate jdbcTemplate;

    @Autowired
    private StudentMapper studentMapper;

    @TargetDataSource(name="ds2")
    public List<Student> likeName(String name){
        return studentMapper.likeName(name);
    }

    public int testSave(){
        Student stu = new Student();
        stu.setAge(33);
        stu.setName("測试新增");
        stu.setSumScore("66");
        stu.setAvgScore("22");
        return studentMapper.insert(stu);//这里调用的是基础Mapper中的insert方法
    }

}

最后另一点要说明，使用公共Mapper“可能”须要对实体类进行改动。假设你的实体字段和数据库字段不一致（或者实体名称和数据库表名不一致），这样才须要改动。比如：

/**
 * 学生实体
 *
 * @author   单红宇(365384722)
 * @myblog  http://blog.csdn.net/catoop/
 * @create    2016年1月12日
 */
public class Student implements Serializable{

    @Id
    private int id;
    private String name;
    @Column(name="SCORE_SUM")
    private String sumScore;
    @Column(name="SCORE_AVG")
    private String avgScore;
    private int age;

    // getter setter 

}

其它没有什么可说的了，请至少要到 https://github.com/abel533/Mapper 把插件的其它说明再看一遍。